1. Field of the Invention
This invention generally relates to an apparatus and method for local video detection for mixed cadence sequence, and more particularly to a pixel-based Local Video Detection (LVD) method and system used as part of the Local Film Mode Detector (LFMD), or part of the de-interlacer, or part of the picture quality enhancement in TV and Set-Top-Box products.
2. Relevant Background
Interlaced video was used for cathode ray tube (CRT) displays and is found throughout a number of broadcasting formats. Modern video displays, e.g., liquid crystal displays (LCD) and plasma displays, do not operate in interlaced mode. Therefore, de-interlacing circuitry is needed in set-top-box (STB)/TV to de-interlace video into progressive video that can be played on modern video displays.
Currently, there are a number of different source formats. Video formats usually display at 50 or 60 frames per second; film formats are commonly captured at 24 or 25 frames per second. Because of the difference is frame rate, telecine is applied to a film source video in order to properly display the film source video on a video display. Reverse telecine may be applied to the telecined film source video to recover a higher quality non-interlaced video to display on a compatible device, such as a modern video display.
U.S. patent application Ser. No. 12/978,154, “Apparatus and Method for Exotic Cadence Detection,” discusses an apparatus and method for exotic cadence detection. Cadence detection finds the source format of a sequence of video fields or detects the absence of motion between frames (still pictures) and determines whether a video is originally from a video or film source that had interlacing or telecine applied. After that, de-interlacing or inverse telecine can be appropriately applied to the video.
Cadence detection systems in the related art have limited applicability to broadcasted videos. Broadcasted videos commonly consist of mixed video and film sources, for example, graphics overlay on a video source, or scrolling text on a film source. Applying either de-interlacing or inverse telecine to mixed cadence sources is suboptimal because de-interlacing compromises vertical resolution on the telecined parts and inverse telecine leaves unhandled feathering or combing artifacts on the interlaced parts.
U.S. Patent Publication No. 2007/0291169, “Region-Based Cadence Detector,” discusses blocked based film/video decision and switching. A frame is segmented into a pre-set number of regions (or clusters of blocks) for cadence and phase tracking. Region-based cadence detection suffers in picture quality and robustness due to artifacts from the switching.
Accordingly, there is a need in the art for an accurate, robust, and efficient mixed film/video mode cadence detection system.